The present disclosure relates to a battery, a battery pack, an electronic apparatus, an electrically driven vehicle, an electrical storage device, and an electric power system.
In recent years, portable electronic apparatuses such as camera-integrated VTRs (Video Tape Recorder), cellular phone, and notebook PCs have become widespread, and a reduction in size, weight, and thickness, and a longer operational lifespan have been strongly desired. Along with this, the development of a battery as a power supply, particularly, a secondary battery, which is light in weight, and which can obtain a high energy density, has been progressed.
Among these, a secondary battery (a so-called lithium ion secondary battery) using occlusion and emission of lithium (Li) in a charge and discharge reaction may obtain an energy density higher than that of a lead battery or a nickel cadmium battery, and thus has been greatly anticipated. As this secondary battery, a laminated film type battery in which an electrode body is packaged with a laminated film to realize a reduction in weight and thickness has been widely used.
This laminated film type battery is light and thus energy density is large. However, accompanying deformation of an exterior packaging member due to gas generation or the like inside the battery, liquid leakage or the like becomes problematic in a case where an electrolyte composed of a fluidic electrolyte similar to an electrolytic solution in the related art is used. As a method of solving this problem, using of a non-fluidic electrolyte has attracted attention in the laminated film type battery. In a battery using the non-fluidic electrolyte, the liquid leakage is less concerned and stability increases, and thus there is an advantage in that a light and thin material such as an aluminum laminated film may be used for an exterior packaging member.
However, in recent electronic apparatuses, since there is a tendency for high-performance and multi-function to further progress, charging and discharging of the secondary battery is frequently repeated, and thus charge and discharge capacity has a tendency to decrease. Particularly, deterioration is significant in a low-temperature environment, and thus an improvement in the battery characteristics is further desired. In addition, in electrical storage usage for a vehicle or electric power equalization, the battery may be used in an environment in which an ambient temperature is low, and thus an improvement in battery characteristic is desired.
In the secondary battery using the non-fluidic electrolyte, these characteristics are particularly problematic. That is, in the electrolytic solution having fluidity of the related art, migration of ions in a liquid becomes easy. Conversely, ion conductivity decreases in the non-fluidic electrolyte due to the viscosity thereof. In addition, in a case where a highly deformable exterior packaging material is used for the laminated film, there is a problem in that an electrode body has a tendency to deform, and thus adhesiveness between electrodes decreases, and a battery characteristic further deteriorates. This tendency becomes more significant in a battery using a laminated electrode body in which sheet-shaped electrodes are laminated.
To improve this performance, Japanese Unexamined Patent Application Publication Nos. 08-511274 and 2009-70636 suggest a technology of using ionic liquid (bis(fluorosulfonyl) imide or the like is used as an anion) as an electrolytic solution. Japanese Unexamined Patent Application Publication Nos. 08-511274 and 2009-70636 disclose a method in which charge transfer resistance in a battery is decreased by using the electrolytic solution, and thus an output characteristic and a cycle characteristic of a battery are improved.
In addition, Japanese Unexamined Patent Application Publication Nos. 2004-165151 and 2010-129449 disclose a technology of using an electrolyte in which a compound that forms a film called an SEI (Solid Electrolyte Interface) on an electrode during charging and discharging of a battery at an initial period of use is added into a solvent in advance. Japanese Unexamined Patent Application Publication Nos. 2004-165151 and 2010-129449 disclose a method in which an electrode surface is stabilized by forming the SEI on the electrode, and thus a decrease in the output characteristic and the cycle characteristic of a battery is suppressed.